Peripheral blood smear of a normal patient (top left)vsBlood smear of someone with a myelodysplastic syndrome that affects the RBCs. Very bizarre RBCs of both size and shape.

Evidence of ineffective hematopoiesis (anemia, neutropenia, thrombocytopenia)Hypercellular marrow <20% blasts (may also rarely be hypocellular)Evidence of dysplasia on BM examination (typically in more than one lineage)Careful exclusion of "mimickers," which are diseases that may look like myelodysplasias